[PATCH v2 0/2] riscv: dts: sophgo: Milk-V Duo 256M ethernet support

[Chen-Yu Yeh <chenyou910331@gmail.com>]

The Milk-V Duo 256M has no Ethernet connector of its own; the SG2002's
internal PHY is only usable through the optional USB & Ethernet IO
board. This series adds an overlay for that board and fixes the name of
the internal PHY node it exposes.

Changes in v2:
 - Enable Ethernet through an overlay instead of in the board
   devicetree, since without the IO board the pins may be used as GPIO
   (Inochi)
 - Send both patches in one thread (Inochi)
 - Test link-up and traffic on the IO board, which v1 could not
 - Collect Inochi's Reviewed-by on the PHY node name fix

The overlay has the same shape as Hiago's for the Milk-V Duo [1], so the
two boards stay consistent. The PHY node name fix is in cv180x.dtsi and
so covers that board as well.

Testing, with a kernel built from this branch:

 - sg2002-milkv-duo256m-eth.dtb: eth0 comes up at 100Mbps/Full, gets an
   address via DHCP and passes traffic
 - sg2002-milkv-duo256m.dtb: no eth0 is created, and the gmac node
   reads back as disabled
   
Kernel log with sg2002-milkv-duo256m-eth.dtb:

  [    1.426499] stmmaceth 4070000.ethernet: User ID: 0x10, Synopsys ID: 0x37
  [    1.426536] stmmaceth 4070000.ethernet: 	DWMAC1000
  [    6.052829] stmmaceth 4070000.ethernet eth0: PHY [mdio_mux-0.0:01] driver [Generic PHY] (irq=POLL)
  [    8.138131] stmmaceth 4070000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx

  # ip addr show eth0
  2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
      inet 192.168.0.47/24 brd 192.168.0.255 scope global dynamic noprefixroute eth0

With the base sg2002-milkv-duo256m.dtb:

  # ip addr show eth0
  ip: can't find device 'eth0'
  # cat /proc/device-tree/soc/ethernet@4070000/status
  disabled

iperf3 against a desktop on the same switch gives 94 Mbit/s with the
board sending and 70-74 Mbit/s with it receiving, with no
retransmissions either way. The receive side being slower is not a CPU
limit on the board; I have not looked into it further yet.

v1: https://lore.kernel.org/sophgo/20260803163323.74414-1-chenyou910331@gmail.com/
    https://lore.kernel.org/sophgo/20260803163427.74445-1-chenyou910331@gmail.com/

[1] https://lore.kernel.org/sophgo/20261001-milkv-duo-eth-overlay-v1-1-78bc1454f35b@baylibre.com/

Chen-Yu Yeh (2):
  riscv: dts: sophgo: add Milk-V Duo 256M ethernet support overlay
  riscv: dts: sophgo: cv180x: Fix internal ephy node name

 arch/riscv/boot/dts/sophgo/Makefile             |  3 +++
 arch/riscv/boot/dts/sophgo/cv180x.dtsi          |  2 +-
 .../dts/sophgo/sg2002-milkv-duo256m-eth.dtso    | 17 +++++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/boot/dts/sophgo/sg2002-milkv-duo256m-eth.dtso

-- 
2.43.0